The present invention relates to an internal combustion engine that has at an end of a camshaft a variable valve timing mechanism for varying a valve timing depending upon a variation of oil pressure.
An internal combustion engine that has at an end of a camshaft for driving an intake valve and/or exhaust valve a variable valve timing mechanism that is actuated by oil pressure for varying a valve timing of the intake valve and/or exhaust valve is known and suited for automotive vehicles. In an internal combustion engine disclosed in Japanese Patent Provisional Publication No. 4-109007, an oil pressure control valve for controlling the oil pressure of a variable valve timing mechanism is positioned higher than a camshaft that is formed with an oil passage in communication with the variable valve timing mechanism so that air bubbles are not contained in the hydraulic oil to be supplied to the variable valve timing mechanism.
Further, in the internal combustion engine disclosed in the above-described Japanese Patent Publication, a head cover (cam carrier) that covers an upper portion of a cylinder head at which the camshaft is provided is formed integral with cam brackets that cooperate with the cylinder head to rotatably support therebetween the camshaft. Namely, the cam brackets to be fixed to the cylinder head while interposing therebetween the camshaft are formed integral with the head cover.
In general, the head cover is attached to the cylinder head in a floating state mainly for suppressing transmission of vibrations from the cylinder head side. However, in case a head cover has a plurality of integral cam brackets as disclosed in Japanese Patent Publication No. 4-109007, it is required that the head cover be firmly fastened at those bracket portions to the cylinder head, thus making it difficult to attain the floating structure and possibly deteriorating the sound and vibration isolation ability. Further, the integral cam brackets requires the head cover to have an increased strength and rigidity, thus resulting in an increased weight and thickness of the head cover.
It is accordingly an object of the present invention to provide an internal combustion engine that is free from the above noted problems.
According to an aspect of the present invention, there is provided an internal combustion engine comprising a camshaft that drives an engine valve, a cam bracket fixed to a cylinder head and rotatably supporting therebetween the camshaft, a head cover that covers an upper portion of the cylinder head at which the camshaft and the cam bracket are provided, a variable valve timing mechanism provided at an end of the camshaft and actuated by oil pressure for varying a valve timing, an oil pressure control valve that controls the oil pressure, and an oil passage fluidly connecting between the oil pressure control valve and the variable valve timing mechanism, wherein the oil pressure control valve is installed on the head cover, and wherein the oil passage includes a first oil passage section formed in the camshaft and in communication with the variable valve timing mechanism, a second oil passage section formed in the head cover and in communication with the oil pressure control valve, and a third oil passage section formed in the cam bracket and providing communication between the first oil passage section and the second oil passage section.
According to a further aspect of the present invention, there is provided an internal combustion engine comprising a camshaft that drives an engine valve, a variable valve timing mechanism provided at an end of the camshaft and actuated by oil pressure for varying a valve timing, an oil pressure control valve that controls the oil pressure, and a pair of oil passages extending through at least the camshaft and fluidly connecting between the oil pressure control valve and the variable valve timing mechanism, wherein an axis of the oil pressure control valve crosses an axis of the camshaft nearly at right angles.